If you want to try one more time here is a custom world guaranteed to be made with the newest PC version, which usually creates several 4x4 sites like you described (although it may take a lot of tries for the game to create), and also lots of sand for glassmaking, if it's any help. It's what I personally use and tweak for all my forts.
[WORLD_GEN]
[TITLE:WORLD OF BEASTS]
[DIM:129:129]
[END_YEAR:1050]
[BEAST_END_YEAR:2:60]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:1]
[ELEVATION:1:400:1600:1600]
[RAINFALL:0:100:1600:1600]
[TEMPERATURE:-50:200:50:400]
[DRAINAGE:0:100:1600:1600]
[VOLCANISM:5:100:1600:1600]
[SAVAGERY:20:100:1600:1600]
[ELEVATION_FREQUENCY:1:0:0:0:0:0]
[RAIN_FREQUENCY:1:10000:0:0:0:10000]
[DRAINAGE_FREQUENCY:1:10000:0:0:0:0]
[TEMPERATURE_FREQUENCY:5:0:0:1:1:1]
[SAVAGERY_FREQUENCY:1:0:0:0:0:10000]
[VOLCANISM_FREQUENCY:1:0:0:0:1:4]
[GOOD_SQ_COUNTS:1:20:50]
[EVIL_SQ_COUNTS:500:1000:16630]
[PEAK_NUMBER_MIN:0]
[OCEAN_EDGE_MIN:0]
[VOLCANO_MIN:0]
[REGION_COUNTS:SWAMP:1000:0:1]
[REGION_COUNTS:DESERT:200:0:0]
[REGION_COUNTS:FOREST:500:0:0]
[REGION_COUNTS:MOUNTAINS:0:10:10]
[REGION_COUNTS:OCEAN:0:0:0]
[REGION_COUNTS:GLACIER:0:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:0:0:0]
[REGION_COUNTS:HILLS:0:0:0]
[EROSION_CYCLE_COUNT:1000]
[RIVER_MINS:150:800]
[PERIODICALLY_ERODE_EXTREMES:1]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:5000]
[CAVE_MIN_SIZE:5]
[CAVE_MAX_SIZE:25]
[MOUNTAIN_CAVE_MIN:25]
[NON_MOUNTAIN_CAVE_MIN:50]
[ALL_CAVES_VISIBLE:1]
[SHOW_EMBARK_RIVER:2]
[SHOW_EMBARK_POOL:2]
[SHOW_EMBARK_M_POOL:2]
[SHOW_EMBARK_M_PIPE:2]
[SHOW_EMBARK_CHASM:2]
[SHOW_EMBARK_PIT:2]
[SHOW_EMBARK_OTHER:2]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:20]
[TOTAL_CIV_POPULATION:-1]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:2080:4000:2080]
[RAIN_RANGES:2080:4000:4000]
[DRAINAGE_RANGES:4000:2000:2080]
[SAVAGERY_RANGES:2080:4000:2080]
[VOLCANISM_RANGES:2080:4000:2080]
Sorry for the nooby question, but where do you insert that? The advanced parameters for designing a new world, or do you copypaste it into a folder somewhere?
Disregard that, I eventually found it after digging around the wiki for some time...
In an attempt to be at least a little on topic, I find that the underground river is very annoying if you try to do water-driven anything, since trees start growing in the canals... That clogged up a couple of perpetual motion machines for me.
I wonder if I'm doing something wrong with the worldgen, though, since I still don't get any neighboring civilizations except for dwarves...? I need sieges, damnit!